Spain is generally seen as the weaker of the two economies (much
worse unemployment, a higher deficit, a much more fragile banking
system, etc.) so this is surprising. Except the crux of the story
is that Silvio Berlusconi continues to threaten to topple the
Italian government, which is based on a fragile coalition of the
major parties.

Berlusconi's threat is that if he's expelled from the Senate —
over criminal convictions — then his party would withdraw support
for the current Letta government, and that would require new
elections, and new chaos. Hence the switch.